Plasma Display Device and Method of Manufacturing Green Phosphor Material for Plasma Display Device

ABSTRACT

A plasma display device having a panel main body in which a pair of transparent substrates is arranged in opposition so as to form a discharge space between the substrates on at least a front side, barrier ribs are arranged on at least one of the substrates to divide the discharge space into a plurality of spaces, a group of electrodes is arranged on the substrates so as to generate discharge in the discharge space divided with the barrier ribs, and phosphor layers that emit by discharge are provided, in which the phosphor layers are equipped with a green phosphor layer including at least a mixture of Zn 2 SiO 4 :Mn and (Y, Gd)BO 3 :Tb, the surface of the Zn 2 SiO 4 :Mn is coated with magnesium oxide, and the ratio of the Mg element to the Si element on the surface measured with an XPS apparatus is 0.7 to 6.0.

TECHNICAL FIELD

The present invention relates to a plasma display device and a method ofmanufacturing a phosphor material constituting a phosphor layer thereof.

BACKGROUND ART

A plasma display device (below, written as “a PDP device”) has attractedattention as an image display device capable of realizing highdefinition and a large screen in recent years.

A plasma display panel (below, written as “PDP”) is a part where theimages of the PDP device are displayed, and is configured with a frontsubstrate and a rear substrate. The front substrate is configured withdisplay electrodes consisting of a striped transparent electrode and ametal bus electrode formed on a glass substrate, a dielectric layercovering the display electrodes, and a protective layer. On the otherhand, the rear substrate is configured with a striped address electrodeformed on the glass substrate, a ground dielectric layer covering theaddress electrode, barrier ribs formed on the ground dielectric layer,and a phosphor layer formed between each barrier rib.

The front substrate and the rear substrate are sealed by a sealingmaterial formed around their circumference. Then, a discharge gasconsisting of neon, xenon, etc. is sealed into a space between the frontsubstrate and the rear substrate created by the sealing.

A PDP with such a configuration performs image display by dischargingthe discharge gas through a voltage applied to a group of electrodesconsisting of the display electrode, a sustain electrode, and a scanelectrode, to thus excite the phosphor layers in response to ultravioletrays generated by discharge.

The PDP performs a full-color display by performing additive colormixture of so-called three primary colors (red, green, and blue). Inorder to perform this full-color display, the PDP is equipped withphosphor layers that emit in red, green, and blue. The phosphor layer ofeach color is configured by layering the phosphor material of eachcolor.

A surface of Zn₂SiO₄:Mn, which is one of typical green phosphormaterials, is charged negatively. Therefore, positive ions of neon andxenon generated in the discharged gas upon the PDP displaying easilycause an ion collision to the negatively charged Zn₂SiO₄:Mn. The surfaceof Zn₂SiO₄:Mn deteriorates by this collision. Therefore, when the PDPdevice is used for a long time, green luminance decreases due to thedeterioration of the Zn₂SiO₄:Mn.

In order to solve this problem, it is disclosed to layer a film that canmake a positive polarity on the surface of Zn₂SiO₄:Mn with a vapordeposition method and a firing method (for example, refer to PatentDocument 1).

However, because the surface of Zn₂SiO₄:Mn is coated with a filmsubstance that does not emit in layering films with the vapor depositionmethod and the firing method, there is a problem that the luminance ofZn₂SiO₄:Mn decreases.

Further, a PDP is proposed in which phosphor particles for PDP coatedwith a coating film of metal oxide by attaching metal alkoxide on thesurface of the phosphor material such as Zn₂SiO₄:Mn and firing this areused (for example, refer to Patent Document 2).

However, because the metal alkoxide is a compound containing organicsubstances, a carbon-based compound remains on the phosphor surface ifthe firing is not performed sufficiently. This carbon-based compounddecomposes by discharge. In particular, the carbon-based compounddecomposed with long hours of use is released in the discharge space,and the discharge becomes unstable.

Furthermore, a technique of mixing positively charged (Y, Gd)BO₃:Tbhaving the same green color into negatively charged Zn₂SiO₄:Mn has beendevised (for example, refer to Patent Document 3).

However, because there is no change in negative chargeability of thesurface of Zn₂SiO₄:Mn, the decrease of the luminance of Zn₂SiO₄:Mncannot be suppressed.

[Patent Document 1] Unexamined Japanese Patent Publication No. H11-86735

[Patent Document 2] Unexamined Japanese Patent Publication No.H10-195428

[Patent Document 3] Unexamined Japanese Patent Publication No.2001-236893

DISCLOSURE OF THE INVENTION

A PDP device of the present invention is a PDP device having a panelmain body in which a pair of substrates is arranged in opposition so asto form a discharge space between the substrates, barrier ribs arearranged on at least one of the substrates to divide the discharge spaceinto a plurality of spaces, a group of electrodes is arranged on thesubstrates so as to generate discharge in the discharge space dividedwith the barrier ribs, and phosphor layers that emit upon discharge areprovided, in which the phosphor layers are equipped with a greenphosphor layer consisting of a mixture of Zn₂SiO₄:Mn and (Y, Gd)BO₃:Tb,the surface of the Zn₂SiO₄:Mn is coated with magnesium oxide, and theratio of a Mg element to a Si element on the surface measured with anXPS apparatus is 0.7 to 6.0.

With such a configuration, a PDP device can be realized in which aluminance of a green phosphor material consisting of Zn₂SiO₄:Mn is highand decrease of the luminance is small even with long hours of use.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a schematic configuration of electrodes ofthe PDP in an embodiment of the present invention.

FIG. 2 is a partial cross-section perspective view in an image displayregion of the PDP in the embodiment of the present invention.

FIG. 3 is a schematic view showing a configuration of the PDP device inthe embodiment of the present invention.

FIG. 4 is a characteristic chart showing the relationship between theinitial luminance and the Mg/Si ratio of the PDP device in theembodiment of the present invention.

FIG. 5 is a characteristic chart showing the relationship between theluminance sustain ratio and the Mg/Si ratio of the PDP device of theembodiment in the present invention.

REFERENCE MARKS IN THE DRAWINGS

-   100 PDP-   101 Front glass substrate-   102 Rear glass substrate-   103 Sustain electrode-   104 Scan electrode-   105 Dielectric glass layer-   106 MgO protective layer-   107 Adress electrode-   108 Ground dieleceric glass layer-   109 Barrier rib-   110R Phosphor layer (Red)-   110G Phosphor layer (Green)-   110B Phosphor layer (Blue)-   121 Airtight seal layer-   122 Discharge space-   130 Front panel-   140 Rear panel-   150 Driving device-   152 Controller-   153 Display driving circuit-   154 Display scan driving circuit-   155 Address driving circuit

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Embodiment

FIG. 1 is a plan view showing a schematic configuration of electrodes ofthe PDP. PDP 100 is equipped with a front glass substrate (not shown inthe figure), rear glass substrate 102, sustain electrode 103, scanelectrode 104, address electrode 107, and airtight seal layer 121. N ofeach sustain electrodes 103 and each scan electrodes 104 are arranged inparallel to each other. M of address electrodes 107 are arranged inparallel. Sustain electrode 103, scan electrodes 104, and addresselectrode 107 have an electrode matrix of a three-electrode structure,and a discharge cell is formed at a crossing point of scan electrode 104and address electrode 107.

FIG. 2 is a partial cross-section perspective view in an image displayregion of the PDP. PDP 100 is configured with front panel 130 and rearpanel 140. Sustain electrode 103, scan electrode 104, dielectric glasslayer 105, and MgO protective layer 106 are formed on front glasssubstrate 101 of front panel 130. Address electrode 107, grounddielectric glass layer 108, barrier rib 109, and phosphor layers 110R,110G, and 110B are formed on rear glass substrate 102 of rear panel 140.

PDP 100 is completed by pasting front panel 130 and rear panel 140together and sealing a discharge gas in discharge space 122 formedbetween front panel 130 and rear panel 140.

FIG. 3 is a schematic view showing a configuration of the PDP deviceusing PDP 100. PDP 100 configures a PDP device by being connected todriving device 150. Display driving circuit 153, display scan drivingcircuit 154, and address driving circuit 155 are connected to PDP 100.Controller 152 controls a voltage applied to these. An address dischargeis performed by applying a prescribed voltage to scan electrode 104 andaddress electrode 107 corresponding to a discharge cell to be turned on.Controller 152 controls this voltage applied. After that, a sustaindischarge is performed by applying a pulse voltage between sustainelectrode 103 and scan electrode 104. With this sustain discharge,ultra-violet rays are generated at the discharge cell where the addressdischarge is performed. The discharge cell is turned on by emittinglight from a phosphor layer excited by the ultra-violet rays. An imageis displayed by the combination of turning on and turning off each colorcell.

Next, a method of manufacturing PDP 100 is explained with reference toFIGS. 1 and 2. First, a method of manufacturing front panel 130 isexplained. N of each sustain electrode 103 and scan electrode 104 areformed in a strip on front glass substrate 101. After that, sustainelectrode 103 and scan electrode 104 are coated with dielectric glasslayer 105. Furthermore, MgO protective layer 106 is formed on a surfaceof dielectric glass layer 105.

Sustain electrode 103 and scan electrode 104 are formed by firing afterbeing coated with a silver paste with screen printing for an electrodehaving silver as a main component. Dielectric glass layer 105 is formedby firing after being coated with a paste containing a bismuthoxide-based glass material with screen printing. The paste containingthe above-described glass material contains for example 30% by weight ofbismuth oxide (Bi₂O₃), 28% by weight of zinc oxide (ZnO), 23% by weightof boron oxide (B₂O₃), 2.4% by weight of silicon oxide (SiO₂), and 2.6%by weight of aluminum oxide. Furthermore, it is formed by mixing 10% byweight of calcium oxide (CaO), 4% by weight of tungsten oxide (WO₃), andan organic binder (in which 10% of ethyl cellulose is dissolved intoα-terpinenol). Here, the organic binder is that a resin is dissolvedinto an organic solvent, and an acrylic resin other than ethyl celluloseas a resin and butyl carbitol as an organic solvent can be also used.Furthermore, a dispersion agent (for example, glycertriolate) can bemixed into such an organic binder.

A coating thickness of dielectric glass layer 105 is adjusted so as tobe a prescribed thickness (about 40 μm). MgO protective layer 106consists of magnesium oxide (MgO), and is formed so as to be aprescribed thickness (about 0.5 μm) with a sputtering method and an ionplating method for example.

Next, a method of manufacturing rear panel 140 is explained. M ofaddress electrode 107 are formed in a strip by screen-printing a silverpaste for an electrode on rear glass substrate 102 and firing. Grounddielectric glass layer 108 is formed by firing after coating addresselectrode 107 with a paste containing a bismuth oxide-based glassmaterial with a screen printing method. In the same manner, barrier rib109 is formed by firing after applying the paste containing a bismuthoxide-based glass material over and over with a fixed pitch with ascreen printing method. Discharge space 122 is partitioned with thisbarrier rib 109, and a discharge cell is formed. The spacing dimensionof barrier rib 109 is regulated to about 130 μm to 240 μm adapting to afull HD television of 42 inch to 50 inch and a HD television.

Red phosphor layer 110R, green phosphor layer 110G, and blue phosphorlayer 110B are formed in a groove between two adjacent barrier ribs 109.Red phosphor layer 110R consists of a red phosphor material of (Y, Gd)BO₃:Eu for example. Blue phosphor layer 110B consists of a blue phosphormaterial of BaMgAl₁₀O₁₇:Eu for example. Green phosphor layer 110Gconsists of a green phosphor material of Zn₂SiO₄:Mn for example.

Front panel 130 and rear panel 140 produced in such a way are layered inopposition so that scan electrode 104 in front panel 130 and addresselectrode 107 in rear panel 140 lie at a right angle to each other.Glass for sealing is applied on the periphery, and it is fired at about450° C. for 10 minutes to 20 minutes. As shown in FIG. 1, front panel130 and rear panel 140 are sealed by forming airtight seal layer 121.Then, PDP 100 is completed by exhausting discharge space 122 to highvacuum once and then sealing a discharge gas (for example, ahelium-xenon-based, and a neon-xenon-based inert gas) at a prescribedpressure.

Next, a method of manufacturing a phosphor material of each color isexplained. In the present embodiment, the phosphor material manufacturedwith a solid phase reaction method is used.

BaMgAl₁₀O₁₇:Eu, which is a blue phosphor material, is produced with thefollowing method. Barium carbonate (BaCO₃), magnesium carbonate (MgCO₃),aluminum oxide, and europium oxide (Eu₂O₃) are mixed so as to agree witha phosphor composition. It is produced by firing the mixture at 800° C.to 1200° C. in air and further firing at 1200° C. to 1400° C. in a mixedgas atmosphere containing hydrogen and nitrogen.

A red phosphor material (Y, Gd)BO₃:Eu is produced with the followingmethod. Yttrium oxide (Y₂O₃), gadolinium oxide (Gd₂O₃), boric acid(H₃BO₃), and europium oxide (EuO₂) are mixed so as to agree with thephosphor composition. It is produced by firing the mixture at 600° C. to800° C. in air and further firing at 1100° C. to 1300° C. in a mixed gasatmosphere containing hydrogen and nitrogen.

Next, a green phosphor material is explained. In the embodiment of thepresent invention, a mixed body of Zn₂SiO₄:Mn and (Y, Gd)BO₃:Tb is alsoused as a green phosphor material. In the mixed body, Zn₂SiO₄:Mn, one inwhich the surface of Zn₂SiO₄:Mn whose surface is not coated with asubstance (below, written as non-coated Zn₂SiO₄:Mn) is coated withmagnesium oxide is used. This magnesium oxide is applied so that theratio of the Mg element to the Si element constituting a phosphormaterial of Zn₂SiO₄:Mn (below, written as Mg/Si ratio) is controlled tobe 0.7 to 6.0 within 10 nm from the outermost surface of Zn₂SiO₄:Mn.

Here, the Mg/Si ratio can be measured with an XPS apparatus. XPS is anabbreviation of X-ray Photoelectron Spectroscopy, called an x-rayphotoelectron spectral analysis, and a method of investigating the stateof elements within 10 nm from the outermost surface of a substance. TheMg/Si ratio is a value in which the analysis of Mg and Si is performedwith the XPS apparatus and the ratio of these is taken.

Below, a method of manufacturing the green phosphor material in theembodiment of the present invention is explained in detail. Thenon-coated Zn₂SiO₄:Mn is produced using a conventional solid phasereaction method, liquid phase method, and liquid spraying method. Thesolid phase reaction method is a producing method by firing oxides orcarbonated materials, and flux. The liquid phase method is a producingmethod by performing hydrolysis of organic metal salts or nitrates in asolution and performing a thermal process on a precursor of the phosphormaterial generated by adding alkali etc. depending on necessity, andprecipitating. Further, the liquid spraying method is a method ofproducing by spraying a solution containing a raw material of thephosphor material in a heated furnace.

The non-coated Zn₂SiO₄:Mn used in the present embodiment is notespecially affected by the producing method. However, the producingmethod with the solid phase reaction method is described here as oneexample. Zinc oxide, silicon oxide, and manganese dioxide (MnO₂) areused as raw materials.

Zinc oxide and silicon oxide, which are raw materials constituting acomposition of a mother material of the phosphor material Zn₂SiO₄, aremixed. The mixing is performed so that silicon oxide becomes excessiveover a stoichiometric ratio, and an excessive amount is 0.1% by mole to5% by mole. Next, manganese dioxide that becomes a center of theemission is added and mixed at 5% by mole to 20% by mole to Zn₂SiO₄:Mn.Moreover, a mixing amount of zinc oxide is appropriately adjusted sothat the total amount of zinc oxide and manganese dioxide becomes 200%by mole to Zn₂SiO₄:Mn.

Next, this mixture is fired at 600° C. to 900° C. for 2 hours. Thenon-coated Zn₂SiO₄:Mn is produced by milling lightly the fired mixture,performing a sieving, and performing a firing at 1000° C. to 1350° C. innitrogen or in a mixed atmosphere of nitrogen and oxygen.

Moreover, the reason why silicon oxide is mixed excessively over thestoichiometric ratio is that a negative chargeability of the surfacebecomes larger by increasing the ratio of silicon oxide, the adheringproperty increases due to a positive a magnesium ion described below,and along with it, an magnesium oxide coat becomes hard. However, whenit exceeds 5% by mole, luminance of Zn₂SiO₄:Mn becomes low, and when itis less than 0.1% by mole, the effect is not demonstrated. Therefore,the excessive mixing amount of silicon oxide is preferably 0.1% by moleto 5% by mole.

Next, the method of coating the surface of the non-coated Zn₂SiO₄ Mnwith magnesium oxide is explained. Magnesium nitrate is dissolved intowater or an alkali solution at a concentration of 0.4% by weight. Amixed solution is produced by putting the non-coated Zn₂SiO₄:Mn in thedissolved solution, and it is stirred while being heated. When theheating temperature is less than 30° C., a metal salt separates in thesolution. Further, when the temperature exceeds 60° C., Zn₂SiO₄:Mn isdissolved by acid or alkali. Because of this, the heating is performedin the temperature range of 30° C. to 60° C. With this stirring, thecoating is performed by adhering the positive magnesium ion in thedissolved solution to the negative chargeable non-coated Zn₂SiO₄:Mn.This mixed solution is filtered and dried. After that, by firing thisdried substance at 400° C. to 800° C. in air, Zn₂SiO₄:Mn in which thesurface is coated with magnesium oxide (below, described as an Mg-coatedZn₂SiO₄:Mn) is produced. The Mg/Si ratio of this Mg-coated Zn₂SiO₄:Mn is1.7.

Next, a method of producing (Y, Gd)BO₃:Tb is described. (Y, Gd)BO₃:Tb isproduced by mixing Y₂O₃, Gd₂O₃, H₃BO₃, and Tb₂O₅ as raw materials so asto achieve the composition of (Y, Gd)BO₃:Tb constituting a compositionof the mother material of the phosphor, firing at 600° C. to 800° C. inair, and then firing at 1100° C. to 1300° C. in an oxygen-nitrogenatmosphere.

A green phosphor is produced in which (Y, Gd)BO₃:Tb produced in such amanner and Mg-coated Zn₂SiO₄:Mn are mixed at a ratio of 1:1 (below,described as Mg-coated mixed green phosphor). Further, a green phosphoris produced in which (Y, Gd)BO₃:Tb and non-coated Zn₂SiO₄:Mn are mixedat a ratio of 1:1 (below, described as non-coated mixed green phosphor).

Green phosphor layer 110G is formed by layering the bove-describedMg-coated mixed green phosphor. PDP 100 is produced with rear panel 140in which (Y, Gd)BO₃:Eu is layered for red phosphor layer 110R andBaMgAl₁₀O₁₇:Eu for blue phosphor layer 110B. Further, for comparison,PDP 100 formed by layering non-coated mixed green phosphor instead ofMg-coated mixed green phosphor is produced in the same manner.

The PDP device is produced by connecting driving device 150 to this PDP100. In this PDP device, only green phosphor layer 110G is made to emit,and the initial luminance and the luminance sustain ratio after turningon for 1000 hours (below, written as the luminance sustain ratio) aremeasured. The luminance sustain ratio is obtained as follows. Adischarge sustain pulse of a voltage 185V and frequency 100 kHz isapplied alternatively to sustain electrode 103 and scan electrode 104 inthe PDP device continuously for 1000 hours. Only the green phosphorlayer is made to emit in the PDP device after turning on for 1000 hours,and the luminance is measured. The luminance sustain ratio representsthe ratio of the luminance after turning on for 1000 hours to theinitial luminance.

The initial luminance of the PDP device using the Mg-coated mixed greenphosphor is 104.5 when the initial luminance of the PDP device using thenon-coated mixed green phosphor is 100. Further, the luminance sustainratio of the PDP device using the Mg-coated mixed green phosphor is 96.8against 94.0 of the PDP device using the non-coated mixed greenphosphor.

In such a way, by using a green phosphor in which Zn₂SiO₄:Mn is coatedwith magnesium oxide with the producing method in the presentembodiment, the luminance sustain ratio can be improved withoutgenerating luminance decrease.

Table 1 shows characteristics of the Mg-coated Zn₂SiO₄:Mn powder andcharacteristics of the PDP device by the mixed green phosphor using thesame in various producing conditions. Types of magnesium metal salt usedfor coating and its preparing amount (% by weight) and the firingtemperature after coating (° C.) are shown as a producing condition ofthe Mg-coated Zn₂SiO₄:Mn. The Mg/Si ratio of green phosphor particles isshown as a characteristic of powder. Further, the initial luminance andthe luminance sustain ratio of the PDP device produced with greenphosphor particles as a characteristic of the PDP device are shown.

TABLE 1 Producing conditions of Zn₂SiO₄:Mn Magnesium Metal Salt usedFiring Characteristics of Plasma Display Device for coating and itsTemprature Characterristics Luminance sustain ratio preparing amount (%by after coating of Powders Initial after turning on for No. weight) (°C.) Mg/Si Ratio Luminance (%) 1000 hours (%) 1 without coating 0.0 100.094.0 2 Magnesium nitrate: 0.1 400.0 0.7 103.2 95.0 3 Magnesium nitrate:0.2 505.0 1.1 105.6 96.0 4 Magnesium acetate: 1.0 510.0 1.3 104.8 96.2 5Magnesium nitrate: 0.4 520.0 1.7 104.5 96.8 6 Magnesium nitrate: 0.8550.0 2.0 100.8 97.0 7 Magnesium oxalate: 1.0 600.0 2.6 97.7 97.4 8Magnesium oxalate: 2.0 700.0 3.0 95.3 98.2 9 Magnesium acetate: 5.0750.0 4.1 91.1 98.3 10 Magnesium oxalate: 4.0 500.0 6.2 94.5 98.7

The non-coated Zn₂SiO₄ Mn produced by the above-described solid phasereaction method is used as the green phosphor particles to be coated.No. 1 is a result of a phosphor of the non-coated Zn₂SiO₄:Mn. Nos. 2, 3,5, and 6 are results of the Mg-coated Zn₂SiO₄:Mn produced with magnesiumnitrate of a preparing amount of 0.1% by weight to 0.8% by weight to thenon-coated Zn₂SiO₄:Mn. Moreover, the result of the above-describedembodiment is shown in No. 5 in Table 1. Further, Nos. 4, and 9 areresults of the Mg-coated Zn₂SiO₄:Mn produced with magnesium acetate ofthe preparing amount of 1% by weight to 5% by weight. Furthermore, Nos.7, 8, and 10 are results of the Mg-coated Zn₂SiO₄:Mn produced withmagnesium oxalate of the preparing concentration of 1% by weight to 4%by weight. In any of the cases, the coating can be performed with thesame method as the above-described producing method.

FIG. 4 is a characteristic chart showing the relationship between theinitial luminance and the Mg/Si ratio of the Mg-coated Zn₂SiO₄:Mn of thePDP device. As shown in FIG. 4, the initial luminance can be increasedcompared to the case of the non-coated Zn₂SiO₄:Mn where the Mg/Si ratiois in the range of 0.7 to 2.0. However, the initial luminance decreaseswith the Mg/Si ratio exceeding 2.0. When the Mg/Si ratio is 6.0 or less,the decrease of the initial luminance is about 15% and there ispractically no problem.

FIG. 5 is a characteristic chart showing the relationship between theluminance sustain ratio and the Mg/Si ratio of the PDP device. As shownin FIG. 5, without relating to the type of the metal salt used in thecoating, when the Mg/Si ratio is 0.7 or more, the luminance sustainratio after turning on for 1000 hours improves compared to the case ofusing the non-coated Zn₂SiO₄:Mn. In particular, when the Mg/Si ratio is1.3 or more, the luminance sustain ratio improves largely. Further, inany of the cases, a change cannot be observed at all in the stability ofdischarge of the PDP device after turning on for 1000 hours.

Therefore, the Mg/Si ratio of the magnesium oxide coating to Zn₂SiO₄:Mnis desirably 0.7 to 6.0 because the luminance has practically no problemand the luminance sustain ratio is improved. Further, the Mg/Si ratio ismore desirably 1.3 to 2.0 because the initial luminance is high and theluminance sustain ratio can be improved largely.

With a conventionally known vapor deposition method and firing method,by performing a finer or thicker coating with Mg, an emitting part onthe phosphor surface is covered up with the coating substance, and theluminance decreases. This is considered to be because the coating withMg is performed over entire particles. Contrary to that, because siliconis detected within 10 nm from the outermost surface by measurement withthe XPS apparatus in the manufacturing method in the present invention,at least a part of the surface is coated without coating the entireparticles. Therefore, the decrease of the luminance is suppressed.Besides, the improvement of the chargeability is performed evenpartially coated, and a sufficient effect is achieved to suppress thedeterioration of the luminance.

Moreover, because an organic substance such as metal alkoxide is notused, there is no cause of unstabilizing the discharge in the inside ofthe PDP, and the discharge stability does not change also over longhours of use.

In the present embodiment, a green phosphor is used in which (Y,Gd)BO₃:Tb and Al-coated Zn₂SiO₄:Mn are mixed at a ratio of 1:1. When themixing ratio is other than 1:1, the effect of the Mg-coated Zn₂SiO₄:Mnis achieved depending on the mixing ratio, and its effect is not limitedto the mixing ratio.

INDUSTRIAL APPLICABILITY

The present invention can realize a PDP device with a smalldeterioration of luminance against a discharge for a long period, and isuseful in a display device of a big screen.

1. A plasma display device comprising: a pair of substrates confrontingeach other so as to form a discharge space between the substrates; abarrier rib arranged on at least one of the substrates to divide thedischarge space into a plurality of spaces; a group of electrodesarranged on the substrates so as to generate discharge in the dischargespace divided with the barrier rib; and a phosphor layer, which emitslight by discharge, on the substrate, wherein the phosphor layer isequipped with a green phosphor layer including a mixture of Zn₂SiO₄:Mnand (Y, Gd)BO₃:Tb, a surface of the Zn₂SiO₄:Mn is coated with magnesiumoxide, and the ratio of an Mg element to a Si element on the surfacemeasured with an XPS apparatus is not less than 0.7 nor more than 6.0.2. The plasma display device according to claim 1, wherein the ratio ofthe Mg element to the Si element is not less than 1.3 nor more than 2.0.